US1782686A - Process for cracking hydrocarbon oil - Google Patents

Description

Nov. 25, 1930. J. G. HAWTHORNE PROCESS FOR CRACKING HYDROCARBON OIL Filed yJuly 9, 1927 Nw. wr D\ w K nuoaU QN v QN Q NN n b nu@ Lm NN. m, n MM s WM m N nu u MN n.. s wk n N Qn b, m Q Q Nn um N 4 m. QN VQ, o Nw. WN wm\ o N ww QN 5N S1 w I NVENTOR Joseph G Hav/(horn, BY ATTOR Patented Nov. 25, 1930 IUNITED sTATEs PATENT oEFicE JOSEPH Gr. HAWTHORNE, 0F KANSAS CITY, AMISSOURI, ASSIGNOR TO WALTER MARTIN y I CROSS PROCESS FOR CRACKING HYDBOCARBON OIL Application nieu my s, i927. serial No. 204,599.

This invention relates to improvements in a process for cracking hydrocarbon oil and.

has for its principal novelty the ideas of reheatinr or superheating hydrocarbon vapors after ttliey'have been raised to a vaporizing temperature in an initialheating stage, whereby a major portion of the cracking or conversion is accomplished while the oil is in a Vaporous or gaseous condition.

A further novelty in the invention lies in the eoolin of the cracked products subsequent to t 1e reheating stage, in Vorder that the cracked material is reduced in temperature sullicient to produce the desired sep-aration of the heavier fractions from the lighter fractions.- This separation is effected by the condensation or liquefaction of t e heavier fractions and the diversion of the same from the system, while the lighter fractions are carried, on to be thereafter subjected toa dephlegmating action and to final condensation.

In addition to the above the maintenance of an equalized pressure in the material conltained vin the conduits in the reheating or ysuperheating stage and the combustion gases surrounding these conduits a'fords a condition which permits the use of highly refractory materials in the reheating or sup'erheating stage, .capable of withstanding the encessive temperature .conditions maintained therein.

The single figure is a diagrammatic side elevational view of one form of apparatus in which the invention may be practiced, with parts shown in section.

Referring to the drawings, at 1 is shown a 'furnace divided by a central baflie Wall 2 separating the furnace into a radiant heatin chamber 3 and a convection heating chamber 4. Heating tubes 5 are arranged along the inside surface of the radiant tube chamber, whilea bank of tubes 6 is positioned within the chamber 4. The tubes are serially connected to form a continuous flow of the oil from the inlet pipe 7 to the outlet or transfer line 8.

The transfer pipe 8 communicates with the header 9 of the reheater considered as a whole as 10. The header 9 of the reheater or superheater functions vas an expansion chamber for the hydrocarbons discharged from` the furnace.- This header communicateswith a second headerfll onthe opposite' side of the reheater tlirou h the tubes or conduits 12. Centrally of t e reheater is positioned a separatin wall 13, which' serves to divide the heating c amber into se arate compartments and supi-port the con uits. The reheater is top ire by means of burners 14, supplied by fuelthrough the pipes 15 and air through the lines 16a. Any type of fuel may beus'ed, either liquid, powdered coal, or gas taken from the gas separator at' the end of the system. Air to the burners is forced by means of an air pumping system to the respective burners, consisting of air fans or pumps 16 receiving their air supply through .the pipes 17. A by-pass 18 with a relief valve 19 is furnished to the separate air supply system. Abreeching or insulated duct 20 connects the reheater with the radiant heat chamber of the furnace 1. lhe passage of gases through the duct is controlled by means of a damper 21, manipulated by a diaphragm valve 22 which is connected to 'a line 23, com- Y municating between the header 9 and one or both of the compartments 24 by a pipe 25 through which the combustion gases pass in their circulation around the conduits 12. The diaphragm valve 22 manipulates the' damper 21 through a connection 26. The

purpose ofy this diaphragm valve, and its connection with the reheater, both internally and externally, is to nlaintain an equalized or a balanced pressure between the gases passing through the conduits in the reheating stage and the combustion gases surrounding the conduits in the reheating stage.

A large vapor' ypipe 27 connects Vthe reheater to a separator 29. Interposed in the vapor pipe is a heat exchanger 30. From the bottom of the separator is a withdrawal line 31, controlled automatically vby' a liquid level regulating device 32 manipulating the valve 33. a An overhead line 34, directs the vapor dischargefrom the separator into the lower or bottom portion of the depegmating tower ab 10 35. This tower is prefer y o\f the bubble line 44 from the top of type, and has in the top a closed coil 36 for preheating the charging stock. A. draw-od1 37, connected into the bottom of the tower, feeds the pump 38 which discharges the refluxcd condensate through a line 39, thence to the suction line 40 of the pump 41 from which it is discharged through the line 7 to the heating tube. In this particular hookup the pump 38 will function as a low pressure pump, and the pump 41 as a high pressure feed pump for the system. The withdrawal of liquid from the reluxing tower 35 is controlled by a liquid level device 42, which manipulates the valve 43 in the line 37. A vapor the tower 35 directs the vapor to a final condensing stage or coil 45, from which the liquid distillate and gas is discharged through the line 46 into the gas separator 47.

Gas from the separator is taken off through the pipe 48, regulated by a valve 49 to be scrubbed or returned to the burners 14 to be used as fuel in the system. Liquid from the separator is withdrawn through the pipe 50 controlled by the liquid level regulating device 51.

In operation the charging'stock to be treated is introduced from any convenient source through the pipe 52, and is charged by means of the pump 53 through the line 54 by means Y of which it is introduced into the closedcoil 36 positioned in the top of the dephlegmating tower. Here the oil, while being preheated, functions as a partialcondenser, separating out the higher boiling point fractions from the hydrocarbon vapors, and thereby assisting the d'ephlegmator or bubble tower in its reiluxing action.

The preheated oil passing from the coil 36 is directed through the line 55, thence through the pipe 56 to the heat exchanger 30. vIn the heat exchanger the oil is brought in heat exchanging relation with the vapor passinor through the pipe 27, and is further preheater. On discharge from the heat exchanger the oil travels through the line 57 and pipe 58 to the suction side of the pump 41.

In case it is desired to fby-pass the heat exchanger the valve 59 is closed and the valve 60 in the line 61 opened, also the valve 62 in the line 57 is closed permitting the oil to pass directly from the pipe 55 through the line 61 into the pipe 58.

In place of the oil being circulated through the heat exchanger, water may be used by introducing the same through the pipe 63, regulated by a valve 64, and dischargingit through the outlet pipe 65 regulated by a valve-66. During the operation, when the water is used as a cooling medium, the oil will be by-passed in the manner explained. In place of water, an extraneous oil, or any other suitable liquid, may be used.

A definite control of the temperature ofthe heat vexchanger is essential'in order that the Maaate hydrocarbons as charged to the separator may be at a temperature Within the range at .whichthe heavier hydrocarbons will be sep arated out as liquid and the lighter fractions pass overhead in the form of vapor.

Returning to the operation the charging stock supplied to the high pressure pump 41 is directed through the line 7 into the bank of coils 6 in the chamber 4 of the furnace 1. After circulation therethrough it passes through the transfer line 67 into the tubes 5. rlhese tubes, as explained, receive the radiant and convection heat of the chamber 3 created by the combustion of fuel burned in the reheater which may or may not be supplemented by an auxiliary burner (33.

The hydrocarbons passing from the furnace through the transfer line 8 are heated to a vaporizing temperature, and at the valve 69 pressure is reduced. At this point steam, either superheated o1' otherwise, is charged to the system through the line 70, regulated by a valve 71 in quantities sufficient to prevent the accumulation of free carbon to an objectionable degree in the reheater..

Normally the discharge temperature from the primary heating stage will be in the neighborhood of from 800 to 1000 F., and the pressure will range from atmospheric pressure to 1000 pounds per square inch.

In the reheating stage the varporized hydrocarbons will receive additional heat so that the discharge from the reheater will normally range from 900 to 1200 F. The pressure in the reheating stage is at all times equalized or balanced with the pressure/ of the combustion gases in the combustion space surrounding the tubes 12. This equalizing of the pressure permits the use of refractory materials in the tube construction such as carborundum, ceramic fire resisting materials, or non-oxidizing metals such as high alloys of chromium, a undum, and other materials of similar characteristic.

On discharge from the reheater the vapors are cooled in the exchanger to temperatures ranging from 700 to 800 F.; a typical temperature at the discharge from the heat exchanger being 7 50 F. This temperature may be varied according to the character of the separation desired in the separating tower 29. As an example, if an increased bottom fraction is desired, this temperature will be lowered While it will `be raised in case a greater percentage of overhead material is required. i

The bottom fraction from the tower 29 is withdrawn and diverted from the system through the pipe 31 while the overhead-material is directed through the line 34 into the bottom of the dephlegmator 35n In the tower 35 the vapors are subjected to a refiuxing action during which a reflux condensate is separated and returned through the line 37 to the system to be retreated, while the vapors are taken off overhead through` the gooseneck 44. These vapors pass to a final condensing stage 45, and are discharged with the gas into the separator 47 from which lthe liquid is withdrawn to the pipe 50 and heat. The particular method here described, i

however, in utilizing a balanced pressure be# tween the gases' contained in the conduits in the reheating stage and the combustion gases circulating outsideof the conduits, has not, as far as is known, been shown in the prior art, or has it been practiced up to this time. In addition to this the control of the discharge temperature and regulation within a proper range to produce the desired res'ililtant products is a further factor of nove ty.

In the event that it is desired to cut out the reheating chamber from the system there is provided a by-pass line 72, regulated by valve 7 3. There is also a valve 74 in the transfer line 8 to prevent the flow of heated oil through the line and cause the'same to pass through the line 72. A valve in the vapor pipe 27 prevents the heated oil directed through the line 7-2 from backing up through the heat exchanger rather than passing directly into the separator 29. By the use of the by-pass line 72 the reheating chamber can be temporarily cut out of the system for cleaning or repairs.

I claim as my invention:

l. A method of cracking hydrocarbon material which consists in raising the oil to a conversion and vaporizing temperature in a primary heating zone, reheating and superheating the vaporized products under reduced pressure in conduits in a separate zone, cooling the vapors to a predetermined tem perature selected to eect separation of the heavier liquid and lighter vapor constituents in a separating stage, subjecting the'vapor constituents to a reflux condensing action, finally condensing vapors not condensed dur ing said reflux condensing step and diverting the heavier liquid divided out in the separating stage from the system, maintaining a balanced pressure between the hydrocarbon vapors Within the conduits in the super' heating zone and the combustion gases in the enclosure surrounding said conduits.

2. A method of cracking hydrocarbon material, which consists'in raising the oil -to a cgnversion and vaporizing temperature in a primary heating stage, reheating and superheating the vaporized products in conduits in a reheating stage, utilizing the heat of the combustion gases discharged from the reheating stage to heat the primary heating stage and maintaining a balanced pressure on the gaseous mixtures inside and outside of the conduits in the reheating stage.

3. A method of cracking hydrocarbon material, which consists in raising the oil to a conversion and vaporizing temperature in a primary heating stage, reheating and superheating the vaporized productslin conduits in a reheating stage, utilizing the heat of the combustion gases discharged from the reheating stage to heat the primary heating stage and maintaining a balanced pressure .i

on the gaseous mixtures inside and o-utside of the conduits in the reheating stage, cooling the hydrocarbon constituents discharged froml the reheating stage and separating the heavier from the light fractions, diverting the heavier fractions from the system as liquid, and subjecting the lighter vapor to refluxing and a final condensing action.

4. A method of cracking hydrocarbon material, which consists in raising the oil to a conversion and vaporizing temperature in a primary heating stage, reheating and superhea-ting the vaporized products in' conduits in a reheating sta-ge, utilizing the heat of the combustion gases discharged from the reheating Stage to heat the primary heating stage and maintaining afbalanced pressure on the gaseous mixtures inside and outside of the conduits in the reheating stage, cooling the hydrocarbon constituents discharged from the reheating stage and separating the heavier from the light fractions, diverting the heavier fractions from the system as liquid, and subjecting the lighter vapor to refluxing and a final condensing ac'- tion, and recycling the reflux condensate to vthe primary heating stage for retreatment.

5. A method of cracking hydrocarbon material which comprises the steps of raising the oil to a conversion and vaporizing temperature in a primary heating zone,reheat ing and superheating the vaporized products in a separate zone, maintaining an equalized pressure between the combustion gases and the material undergoing superheating in the separate reheating zone, cooling the vapor to a predetermined temperature selected to effect separation of the heavier and lighter vapor constituents in a separate stage, reluxing and condensing the lighter materials 'and diverting the heavier liquid products divided out in the separating stage from the system.

JOSEPH G. HAWTHORNE.

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